Many consumers desire to use cosmetic and care compositions that enhance the appearance of keratinous substrates such as hair, e.g., by changing the color, style, and/or shape of the hair, and/or by imparting various cosmetic properties to hair, such as shine and conditioning. Many of the known compositions and processes for enhancing the appearance of hair involve chemical treatments to the hair.
The process of changing the color of hair, for example, can involve depositing an artificial color onto the hair which provides a different shade or color to the hair, and/or lifting the color of the hair, such as lightening the color of dark hair to lighter shades. The process of lifting the color of hair, also known as lightening (or bleaching), generally requires the use of oxidizing agents. Lightening of hair is typically evaluated by the variation in tone height before and after the application of a hair color-altering composition onto hair. This variation corresponds to the degree or level of lightening or lift. The notion of “tone” is based on the classification of the natural shades, one tone separating each shade from the shade immediately following or preceding it, which is well known to hairstyling professionals. The tone heights or levels can range from 1 (black) to 10 (light blond), one unit corresponding to one tone; thus, the higher the number, the lighter the shade or the greater the degree of lift.
In general, hair lightening or color lifting compositions and hair coloring or dyeing compositions possess an alkalinity such that these compositions have a pH value of above 7, typically being at pH 9 and above, and may generally require the presence of an alkalizing agent such as ammonia or an ammonia gas generating compound and/or an amine or ammonium-based compound in amounts sufficient to make such compositions alkaline. The alkalizing agent causes the hair shaft to swell, thus allowing the small oxidative dye molecules to penetrate the cuticle and cortex before the oxidation condensation process is completed. The resulting larger-sized colored complexes from the oxidative reaction are then trapped inside the hair fiber, thereby permanently altering the color of the hair.
Additionally, there are many techniques and compositions for styling or altering the shape of hair. For example, hair care products referred to as “hair relaxers” or “hair straighteners” can relax or straighten curly or kinky hair, including wavy hair. Straightening or relaxing the curls of very curly hair may increase the manageability and ease of styling of such hair. Compositions for permanent waving the hair will impart a curl or a wave to otherwise straight hair. Different types of compositions can be applied onto hair in order to change its shape and make it more manageable, such as alkaline and acidic compositions. Hair relaxers, straighteners, perms, and/or waves may either be applied in a hair salon by a professional or in the home by the individual consumer.
While dyeing or color lifting compositions can effectively alter the color of hair, and relaxing, straightening, perming, and waving compositions can effective alter the shape of the hair, these chemical treatments can damage the hair fibers and/or irritate the scalp. Thus, in order to reduce or avoid damage to hair, as well as to improve the cosmetic performance of the compositions, the use of new and additional components and novel combinations of ingredients are continuously sought.
However, the choice of components or combinations of ingredients could pose difficulties insofar as they cannot be detrimental to other cosmetic attributes such as ease and uniformity of application, rheology or viscosity properties and stability of the compositions, color deposit and target shade formation, and/or result into more disadvantages such as increased damage or a less healthy look to the hair. It would therefore be desirable to provide the consumer with compositions and methods that can chemically treat the hair while providing other cosmetic advantages such as shine, conditioning, fiber strength, and/or a healthy appearance to the hair, but avoiding or minimizing damage to the hair.
Further, both natural and sensitized or chemically treated hair can contain several kinds of negatively charged moieties, for example, carboxylates (resulting from the hydrolysis of amino acids and thioester bonds) and/or sulfonates (resulting from the oxidation of disulfide bonds). These negatively charged moieties can degrade the cosmetic properties of the hair. Moreover, when hair is chemically treated or damaged, the disulfide bonds in hair (disulfide linkages between two cysteine units) can be reduced or broken, resulting in the formation of thiol groups and/or cysteic acid.